Ending up on this page means that you already know that whisper is not that disk space efficient.
Unless you have unlimited disk space, which you don't have, at some point you would want to clean it up.

This is how I am doing it:

1. Delete old metrics of ours that haven't been written to for over 90 days
[codesyntax lang="bash"]

# just to satisfy my curiosity: how much disk space I will gain
find /data/db/whisper/ -name "*wsp" -mtime +90 -exec echo -n -e {}"\0" \; | du -hc --files0-from=-
# delete the files!
find /data/db/whisper/ -type f -mtime +90 -name "*wsp" -exec rm '{}' \;

[/codesyntax]

2. Delete empty directories
[codesyntax lang="bash"]

# how many do we have?
find /data/db/whisper/ -type d -empty | wc -l
# remove them!
find /data/db/whisper/ -type d -empty -delete

[/codesyntax]